The invention relates generally to green emitting phosphors applicable to lighting systems. More particularly, the invention relates to green-emitting phosphors for solid state lighting systems, and a lighting apparatus employing these phosphors and blends thereof.
Generation of “white light” is currently achieved by so called “white LEDs” that are constituted by employing a blue LED in conjunction with a yellow-green emitting, cerium-doped yttrium aluminum garnet known as “YAG,” having the formula Y3Al5O12:Ce3+. YAG has been historically used in these lighting systems because of the high quantum efficiency under blue light excitation and a broad emission spectrum that peaks in the yellow spectral region. The drawback of YAG based lighting systems is the relatively poor color rendering properties and high color temperature. For example, when an object is illuminated under such currently used white LEDs, they cannot imitate the colors illuminated by natural light.
Although numerous phosphors have been proposed in the past several years, the range of phosphors that are suitable for LEDs is limited. Therefore, there is a need for new green-emitting phosphors that produce improved color rendering in white light emitting solid state lighting systems.